Chemical vapor deposition (CVD) is one of the most common deposition processes employed for depositing layers on a substrate. CVD is a flux-dependent deposition technique that uses precise control of the substrate temperature and the precursors introduced into the processing chamber in order to produce a layer of uniform thickness. These requirements become more critical as substrate size increases, creating a need for more complexity in chamber design and gas flow techniques to maintain adequate uniformity.
A variant of CVD that demonstrates excellent step coverage is cyclical deposition or atomic layer deposition (ALD). Cyclical deposition is based upon atomic layer epitaxy (ALE) and employs chemisorption techniques to deliver precursor molecules on a substrate surface in sequential cycles. The cycle exposes the substrate surface to a first precursor, a purge gas, a second precursor and the purge gas. The first and second precursors react to form a product compound as a film on the substrate surface. The cycle is repeated to form the layer to a desired thickness.
Deposition by CVD or ALD, amongst other techniques, uses solid or liquid precursors that sublimated or evaporated for introduction in to the processing chamber. The amount of time required for precursor saturation is a potentially rate-limiting component of the deposition process. Elevated temperatures can be used to decrease the time needed to reach saturation. However, many precursors have poor stability at elevated temperatures. Additionally, many precursors can act as aggressive stainless steel etchants, causing damage to the processing chamber components. Therefore, there is a need in the art for improved precursors for the deposition of metal films.